Support callstack paging

[roblourens]

P2, 1 day?
Currently we only show 20 frames but now the framework supports this

[roblourens]

I don't think we can actually do this with CDP, since we get all the frames at once in the Debugger.paused event. I don't know that it's a problem though.

[auchenberg]

@roblourens Any reason for why we can't show all frames? Rendering perf?

[roblourens]

Sending info across the wire about lots of frames has bogged down the connection in the past, so we have the option to lazy load them. This might have been more of a problem with the legacy node debug protocol connection, than the connection between the debug adapter and vscode, though.